Processes for producing lignin-coated hydrophobic cellulose, and compositions and products produced therefrom

ABSTRACT

Processes disclosed are capable of converting biomass into high-crystallinity, hydrophobic cellulose. In some variations, the process includes fractionating biomass with an acid (such as sulfur dioxide), a solvent (such as ethanol), and water, to generate cellulose-rich solids and a liquid containing hemicellulose and lignin; and depositing lignin onto cellulose fibers to produce lignin-coated cellulose materials (such as dissolving pulp). The crystallinity of the cellulose material may be 80% or higher, translating into good reinforcing properties for composites. Optionally, sugars derived from amorphous cellulose and hemicellulose may be separately fermented, such as to monomers for various polymers. These polymers may be combined with the hydrophobic cellulose to form completely renewable composites.

PRIORITY DATA

This patent application is a continuation application of U.S. patentapplication Ser. No. 15/609,836, filed May 31, 2017, which is acontinuation application of U.S. patent application Ser. No. 14/606,200,filed Jan. 27, 2015, which claims priority to U.S. Provisional PatentApp. No. 61/941,241, filed Feb. 18, 2014 and to U.S. Provisional PatentApp. No. 61/980,996, filed Apr. 17, 2014, each of which is herebyincorporated by reference herein.

FIELD

The present invention generally relates to cellulose and relatedmaterials produced by fractionating lignocellulosic biomass and furtherprocessing the cellulose fraction.

BACKGROUND

Biomass refining (or biorefining) has become more prevalent in industry.Cellulose fibers and sugars, hemicellulose sugars, lignin, syngas, andderivatives of these intermediates are being utilized for chemical andfuel production. Indeed, we now are observing the commercialization ofintegrated biorefineries that are capable of processing incoming biomassmuch the same as petroleum refineries now process crude oil.Underutilized lignocellulosic biomass feedstocks have the potential tobe much cheaper than petroleum, on a carbon basis, as well as muchbetter from an environmental life-cycle standpoint.

Lignocellulosic biomass is the most abundant renewable material on theplanet and has long been recognized as a potential feedstock forproducing chemicals, fuels, and materials. Lignocellulosic biomassnormally comprises primarily cellulose, hemicellulose, and lignin.Cellulose and hemicellulose are natural polymers of sugars, and ligninis an aromatic/aliphatic hydrocarbon polymer reinforcing the entirebiomass network. Some forms of biomass (e.g., recycled materials) do notcontain hemicellulose.

Cellulose or cellulose derivatives can be used in a wide variety ofapplications such as polymer reinforcement, anti-microbial films,biodegradable food packaging, printing papers, pigments and inks, paperand board packaging, barrier films, adhesives, biocomposites, woundhealing, pharmaceuticals and drug delivery, textiles, water-solublepolymers, construction materials, recyclable interior and structuralcomponents for the transportation industry, rheology modifiers,low-calorie food additives, cosmetics thickeners, pharmaceutical tabletbinders, bioactive paper, pickering stabilizers for emulsion andparticle stabilized foams, paint formulations, films for opticalswitching, and detergents.

For some cellulose applications, it would be beneficial to increase thehydrophobicity of the cellulose. Therefore, improved processes areneeded in the art.

SUMMARY

In some variations, the present invention provides a process forproducing a lignin-coated cellulose material, the process comprising:

(a) providing a lignocellulosic biomass feedstock;

(b) fractionating the feedstock in the presence of an acid, a solventfor lignin, and water, to generate cellulose-rich solids and a liquidcontaining hemicellulose and lignin;

(c) depositing at least some of the lignin, from the liquid, onto asurface of the cellulose-rich solids to generate a lignin-coatedcellulose material;

(d) optionally mechanically treating the lignin-coated cellulosematerial; and

(e) recovering the lignin-coated cellulose material,

wherein the cellulose crystallinity of the lignin-coated cellulosematerial is at least 60%, and wherein the lignin-coated cellulosematerial is at least partially hydrophobic.

In some embodiments, the acid is selected from the group consisting ofsulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid,lignosulfonic acid, and combinations thereof. In certain embodiments,the acid is sulfur dioxide. In step (b), exemplary conditions includeSO₂ concentration from about 12 wt % to about 30 wt %, fractionationtemperature from about 140° C. to about 170° C., and fractionation timeis from about 1 hour to about 2 hours.

Step (c) is performed either in the same unit as step (b), such as adigestor, or in another unit. Step (c) may occur sequentially followingstep (b), or simultaneously with step (b), or some combination thereof.Conditions may be selected or optimized to promote deposition of ligninonto the cellulose. For example, longer time, higher temperature, lowerpH, and/or lower concentration of the solvent for lignin may be utilizedto cause or promote lignin deposition during step (c). In someembodiments, conditions of step (c) are different than those of step(b), and physically separate units are employed (or employed in one unitin a batch-wise process). In other embodiments, a single set ofconditions for steps (b) and (c) are selected, and steps (b) and (c) arecombined into a single reactor.

When step (d) is performed, steps (c) and (d) may be integrated so thatsome lignin is physically deposited onto cellulose during mechanicaltreatment. In some embodiments, the lignin-coated cellulose material istreated with a total mechanical energy of less than about 1000kilowatt-hours per ton of the lignin-coated cellulose material, such asless than about 500 kilowatt-hours per ton of the lignin-coatedcellulose material. In certain embodiments, the total mechanical energyis from about 100 kilowatt-hours to about 400 kilowatt-hours per ton ofthe lignin-coated cellulose material.

The process may further include treatment of the lignin-coated cellulosematerial with one or more enzymes or with one or more acids. Such acidsmay be selected from the group consisting of sulfur dioxide, sulfurousacid, lignosulfonic acid, acetic acid, formic acid, and combinationsthereof. Alternatively or additionally, the process may further includetreatment of the lignin-coated cellulose material with heat.

In some embodiments, the cellulose crystallinity of the lignin-coatedcellulose material is at least 70%, such as at least 80% or 85%.

The lignin-coated cellulose material may include or consist essentiallyof lignin-coated dissolving pulp, lignin-coated fibrillated cellulose,lignin-coated microcrystalline cellulose, lignin-coated nanocellulose,or other forms of lignin-coated pulp.

The lignin-coated cellulose material may be characterized by an averagedegree of polymerization from about 100 to about 1500, such as fromabout 300 to about 700 or from about 150 to about 250.

Optionally, the process further comprises hydrolyzing amorphouscellulose, contained in the lignocellulosic biomass feedstock, intoglucose, and optionally fermenting the glucose to a fermentationproduct. Also optionally, the process further comprises recovering,fermenting, or further treating hemicellulosic sugars derived from thehemicellulose.

In certain embodiments, the process comprises fermenting thehemicellulosic sugars to produce a monomer or precursor thereof;polymerizing the monomer to produce a polymer; and combining the polymerand the lignin-coated cellulose material to form a polymer-cellulosecomposite.

In some embodiments, the process further comprises recovering,combusting, or further treating the lignin that does not deposit ontothe cellulose-rich solids during step (c). The process may furthercomprise chemically converting the lignin-coated cellulose material toone or more lignin-coated cellulose derivatives such as celluloseesters, cellulose ethers, cellulose ether esters, alkylated cellulosecompounds, cross-linked cellulose compounds, acid-functionalizedcellulose compounds, base-functionalized cellulose compounds, orcombinations thereof.

Some variations provide a process for producing a hydrophobic cellulosematerial, the process comprising:

(a) providing a lignocellulosic biomass feedstock;

(b) fractionating the feedstock in the presence of an acid, a solventfor lignin, and water, to generate cellulose-rich solids and a liquidcontaining hemicellulose and lignin, wherein a portion of the lignindeposits onto a surface of the cellulose-rich solids, thereby renderingthe cellulose-rich solids at least partially hydrophobic;

(c) optionally mechanically treating the cellulose-rich solids to formcellulose fibrils and/or cellulose crystals, having a crystallinity ofat least 60%; and

(d) recovering the hydrophobic cellulose material.

In some embodiments, the acid is selected from the group consisting ofsulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid,lignosulfonic acid, and combinations thereof.

The crystallinity of the hydrophobic cellulose material may at least 70%or at least 80%. The hydrophobic cellulose material may be characterizedby an average degree of polymerization from about 100 to about 1500,such as about 300 to about 700 or about 150 to about 250.

Optionally, the process further comprises chemically modifying thelignin to increase hydrophobicity of the hydrophobic cellulose material.Such modification to lignin could be done in solution or after thelignin is deposited onto cellulose.

Variations provide a process for producing a cellulose-containingproduct, the process comprising providing a lignin-coated cellulosematerial or a hydrophobic cellulose material, and then incorporating atleast a portion of the lignin-coated cellulose material or thehydrophobic cellulose material into a cellulose-containing product.

In some embodiments, the process comprises forming a structural objectthat includes the cellulose material, or a derivative thereof. Incertain embodiments, the process comprises forming a foam or aerogelthat includes the cellulose material, or a derivative thereof.

In some embodiments, the process comprises combining the cellulosematerial, or a derivative thereof, with one or more other materials toform a composite. The one or more other materials may include a polymerselected from polyolefins, polyesters, polyurethanes, polyamides, orcombinations thereof. The one or more other materials may includecarbon.

In some embodiments, the process comprises forming a film (such as aflexible film) comprising the cellulose material, or a derivativethereof. In some embodiments, the process comprises forming a coating orcoating precursor comprising the cellulose material, or a derivativethereof.

In some embodiments, the cellulose-containing product is configuredelectrochemically for carrying or storing an electrical current orvoltage.

In some embodiments, the cellulose-containing product is incorporatedinto a filter, membrane, or other separation device.

In some embodiments, the cellulose-containing product is incorporated asan additive into a coating, paint, or adhesive.

In some embodiments, the cellulose-containing product is configured as acatalyst, catalyst substrate, or co-catalyst.

In some embodiments, the cellulose-containing product is incorporated asa cement additive.

In some embodiments, the cellulose-containing product is a papercoating.

In some embodiments, the cellulose-containing product is amoisture-barrier pressed pulp product.

In some embodiments, the cellulose-containing product is incorporated asa thickening agent or rheological modifier.

In some embodiments, the cellulose-containing product is incorporated asan additive in a drilling fluid, such as an oil recovery fluid and/or agas recovery fluid.

A hydrophobic cellulose composition is disclosed with a cellulosecrystallinity of about 70% or greater, wherein the hydrophobic cellulosecomposition contains cellulose particles having a surface concentrationof lignin that is greater than a bulk concentration of lignin.

In some embodiments, the cellulose crystallinity is about 75% orgreater, such as about 80% or 80% or greater.

In some embodiments, the hydrophobic cellulose composition furthercomprises sulfur. The sulfur may be derived from the process to producethe hydrophobic cellulose, or otherwise incorporated into thecomposition.

In some embodiments, the hydrophobic cellulose composition ischaracterized by an average cellulose degree of polymerization fromabout 100 to about 1500, such as about 300 to about 700 or about 150 toabout 250. The composition may be characterized by a cellulose degree ofpolymerization distribution having a single peak or two peaks, forexample.

In various embodiments, the cellulose-containing product is selectedfrom the group consisting of a structural object, a foam, an aerogel, apolymer composite, a carbon composite, a film, a coating, a coatingprecursor, a current or voltage carrier, a filter, a membrane, acatalyst, a catalyst substrate, a coating additive, a paint additive, anadhesive additive, a cement additive, a paper coating, amoisture-barrier pressed pulp product, a thickening agent, a rheologicalmodifier, an additive for a drilling fluid, and combinations orderivatives thereof.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts the production of lignin-coated cellulose materials frombiomass, according to some embodiments of the invention. Mechanicaltreatment is optional.

FIG. 2 depicts the production of lignin-coated cellulose materials frombiomass, according to some embodiments of the invention. Mechanicaltreatment and bleaching are both optional.

FIG. 3 depicts the production of lignin-coated cellulose materials frombiomass, according to some embodiments of the invention.

FIG. 4 depicts the production of lignin-coated cellulose materials frombiomass, according to some embodiments of the invention. Mechanicaltreatment is optional.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

This description will enable one skilled in the art to make and use theinvention, and it describes several embodiments, adaptations,variations, alternatives, and uses of the invention. These and otherembodiments, features, and advantages of the present invention willbecome more apparent to those skilled in the art when taken withreference to the following detailed description of the invention inconjunction with any accompanying drawings.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly indicates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as is commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. All composition numbers and ranges based on percentages areweight percentages, unless indicated otherwise. All ranges of numbers orconditions are meant to encompass any specific value contained withinthe range, rounded to any suitable decimal point.

Unless otherwise indicated, all numbers expressing parameters, reactionconditions, concentrations of components, and so forth used in thespecification and claims are to be understood as being modified in allinstances by the term “about.” Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the followingspecification and attached claims are approximations that may varydepending at least upon a specific analytical technique.

The term “comprising,” which is synonymous with “including,”“containing,” or “characterized by” is inclusive or open-ended and doesnot exclude additional, unrecited elements or method steps. “Comprising”is a term of art used in claim language which means that the named claimelements are essential, but other claim elements may be added and stillform a construct within the scope of the claim.

As used herein, the phrase “consisting of” excludes any element, step,or ingredient not specified in the claim. When the phrase “consists of”(or variations thereof) appears in a clause of the body of a claim,rather than immediately following the preamble, it limits only theelement set forth in that clause; other elements are not excluded fromthe claim as a whole. As used herein, the phrase “consisting essentiallyof” limits the scope of a claim to the specified elements or methodsteps, plus those that do not materially affect the basis and novelcharacteristic(s) of the claimed subject matter.

With respect to the terms “comprising,” “consisting of,” and “consistingessentially of,” where one of these three terms is used herein, thepresently disclosed and claimed subject matter may include the use ofeither of the other two terms. Thus in some embodiments not otherwiseexplicitly recited, any instance of “comprising” may be replaced by“consisting of” or, alternatively, by “consisting essentially of.”

Generally it is beneficial to process biomass in a way that effectivelyseparates the major fractions (cellulose, hemicellulose, and lignin)from each other. Fractionation of lignocellulosics leads to release ofcellulosic fibers and opens the cell wall structure by dissolution oflignin and hemicellulose between the cellulose microfibrils. The fibersbecome more accessible for conversion to fibrils or crystals.Hemicellulose sugars can be fermented to a variety of products, such asethanol, or converted to other chemicals. Lignin from biomass has valueas a solid fuel and also as an energy feedstock to produce liquid fuels,synthesis gas, or hydrogen; and as an intermediate to make a variety ofpolymeric compounds. Additionally, minor components such as proteins orrare sugars can be extracted and purified for specialty applications.

This disclosure describes processes and apparatus to efficientlyfractionate any lignocellulosic-based biomass into its primary majorcomponents (cellulose, lignin, and if present, hemicellulose) so thateach can be used in potentially distinct processes. An advantage of theprocess is that it produces cellulose-rich solids while concurrentlyproducing a liquid phase containing a high yield of both hemicellulosesugars and lignin, and low quantities of lignin and hemicellulosedegradation products. The flexible fractionation technique enablesmultiple uses for the products. The cellulose is an advantaged precursorfor producing lignin-coated cellulose, as will be described herein.

The present invention, in some variations, is premised on the discoverythat lignin-coated cellulose and related materials can be produced undercertain conditions including process conditions and steps associatedwith the AVAP® process. It has been found, surprisingly, that very highcrystallinity can be produced and maintained, without the need for anenzymatic or separate acid treatment step to hydrolyze amorphouscellulose. High crystallinity can translate to mechanically strongfibers or good physical reinforcing properties, which are advantageousfor composites, reinforced polymers, and high-strength spun fibers andtextiles, for example.

Using sulfur dioxide (SO₂) and ethanol (or other solvent), thepretreatment disclosed herein effectively removes not onlyhemicelluloses and lignin from biomass but also the amorphous regions ofcellulose, giving a unique, highly crystalline cellulose material thatrequires minimal mechanical energy for reduction of fiber size. The lowmechanical energy requirement results from the fibrillated cellulosenetwork formed during chemical pretreatment upon removal of theamorphous regions of cellulose.

As intended herein, cellulose products may include a range of cellulosicmaterials, including but not limited to market pulp, dissolving pulp,particulated cellulose, fibrillated cellulose, microfibrillatedcellulose, nanofibrillated cellulose, microcrystalline cellulose, andnanocrystalline cellulose.

“Nanofibrillated cellulose” or equivalently “cellulose nanofibrils”means cellulose fibers or regions that contain nanometer-sized particlesor fibers, or both micron-sized and nanometer-sized particles or fibers.“Nanocrystalline cellulose” or equivalently “cellulose nanocrystals”means cellulose particles, regions, or crystals that containnanometer-sized domains, or both micron-sized and nanometer-sizeddomains. “Micron-sized” includes from 1 μm to 100 μm and“nanometer-sized” includes from 0.01 nm to 1000 nm (1 μm). Largerdomains (including long fibers) may also be present in these materials.

As used herein, “lignin-coated cellulose” means cellulose particles orfibers which contain lignin on or near the surface of the particles orfibers. Lignin may also be present in the bulk (internal) portion of thecellulose particles or fibers, but the concentration of lignin at thesurface is higher than the concentration of lignin in the internalportion. Lignin-coated cellulose may be produced according to theprocesses disclosed herein, comprising depositing lignin that has beenfirst solubilized by delignification and then undergoes precipitationonto the cellulose. There may be some chemical changes that take placeupon lignin precipitation (e.g., condensation chemistry) to alterhydrophobicity, molecular weight, sulfur content, oxygen content, —OHgroup content, and so on. The surface coating is not necessarilycontinuous or uniform in chemical composition, hydrophobicity, orthickness.

Certain exemplary embodiments of the invention will now be described.These embodiments are not intended to limit the scope of the inventionas claimed. The order of steps may be varied, some steps may be omitted,and/or other steps may be added. Reference herein to first step, secondstep, etc. is for purposes of illustrating some embodiments only.

In some variations, the present invention provides a process forproducing a lignin-coated cellulose material, the process comprising:

-   -   (a) providing a lignocellulosic biomass feedstock;    -   (b) fractionating the feedstock in the presence of an acid, a        solvent for lignin, and water, to generate cellulose-rich solids        and a liquid containing hemicellulose and lignin;    -   (c) depositing at least some of the lignin, from the liquid,        onto a surface of the cellulose-rich solids to generate a        lignin-coated cellulose material;    -   (d) optionally mechanically treating the lignin-coated cellulose        material; and    -   (e) recovering the lignin-coated cellulose material, wherein the        lignin-coated cellulose material is at least partially        hydrophobic.

In some embodiments, the acid is selected from the group consisting ofsulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid,lignosulfonic acid, and combinations thereof. In certain embodiments,the acid is sulfur dioxide. In step (b), exemplary conditions includeSO₂ concentration from about 12 wt % to about 30 wt %, fractionationtemperature from about 140° C. to about 170° C., and fractionation timeis from about 1 hour to about 2 hours.

Step (c) is performed either in the same unit as step (b), such as adigestor, or in another unit. Step (c) may occur sequentially followingstep (b), or simultaneously with step (b), or some combination thereof.Conditions may be selected or optimized to promote deposition of ligninonto the cellulose. For example, longer time, higher temperature, lowerpH, and/or lower concentration of the solvent for lignin may be utilizedto cause or promote lignin deposition during step (c). In someembodiments, conditions of step (c) are different than those of step(b), and physically separate units are employed (or employed in one unitin a batch-wise process). In other embodiments, a single set ofconditions for steps (b) and (c) are selected, and steps (b) and (c) arecombined into a single reactor.

Conditions to promote deposition of lignin onto the cellulose may beselected according to the Examples and other disclosure in U.S. PatentApp. No. 61/941,215, which is commonly assigned and which has been filedof even date herewith (Feb. 18, 2014). U.S. Patent App. No. 61/941,215is hereby incorporated by reference herein in its entirety.

When step (d) is performed, steps (c) and (d) may be integrated so thatsome lignin is physically deposited onto cellulose during mechanicaltreatment. In some embodiments, the lignin-coated cellulose material istreated with a total mechanical energy of less than about 1000kilowatt-hours per ton of the lignin-coated cellulose material, such asless than about 500 kilowatt-hours per ton of the lignin-coatedcellulose material. In certain embodiments, the total mechanical energyis from about 100 kilowatt-hours to about 400 kilowatt-hours per ton ofthe lignin-coated cellulose material.

The process may further include treatment of the lignin-coated cellulosematerial with one or more enzymes or with one or more acids. Such acidsmay be selected from the group consisting of sulfur dioxide, sulfurousacid, lignosulfonic acid, acetic acid, formic acid, and combinationsthereof. Alternatively or additionally, the process may further includetreatment of the lignin-coated cellulose material with heat.

In some embodiments, the crystallinity of the lignin-coated cellulosematerial is at least 70%, such as at least 80% or 85%.

The lignin-coated cellulose material may include or consist essentiallyof lignin-coated dissolving pulp, lignin-coated fibrillated cellulose,lignin-coated microcrystalline cellulose, lignin-coated nanocellulose,or other forms of lignin-coated pulp.

The lignin-coated cellulose material may be characterized by an averagedegree of polymerization from about 100 to about 1500, such as fromabout 300 to about 700 or from about 150 to about 250.

Optionally, the process further comprises hydrolyzing amorphouscellulose, contained in the lignocellulosic biomass feedstock, intoglucose, and optionally fermenting the glucose to a fermentationproduct. Also optionally, the process further comprises recovering,fermenting, or further treating hemicellulosic sugars derived from thehemicellulose.

In certain embodiments, the process comprises fermenting thehemicellulosic sugars to produce a monomer or precursor thereof;polymerizing the monomer to produce a polymer; and combining the polymerand the lignin-coated cellulose material to form a polymer-cellulosecomposite.

In some embodiments, the process further comprises recovering,combusting, or further treating the lignin that does not deposit ontothe cellulose-rich solids during step (c). The process may furthercomprise chemically converting the lignin-coated cellulose material toone or more lignin-coated cellulose derivatives such as celluloseesters, cellulose ethers, cellulose ether esters, alkylated cellulosecompounds, cross-linked cellulose compounds, acid-functionalizedcellulose compounds, base-functionalized cellulose compounds, orcombinations thereof.

The biomass feedstock may be selected from hardwoods, softwoods, forestresidues, eucalyptus, industrial wastes, pulp and paper wastes, consumerwastes, or combinations thereof. Some embodiments utilize agriculturalresidues, which include lignocellulosic biomass associated with foodcrops, annual grasses, energy crops, or other annually renewablefeedstocks. Exemplary agricultural residues include, but are not limitedto, corn stover, corn fiber, wheat straw, sugarcane bagasse, sugarcanestraw, rice straw, oat straw, barley straw, miscanthus, energy canestraw/residue, or combinations thereof. The process disclosed hereinbenefits from feedstock flexibility; it is effective for a wide varietyof cellulose-containing feedstocks.

As used herein, “lignocellulosic biomass” means any material containingcellulose and lignin. Lignocellulosic biomass may also containhemicellulose. Mixtures of one or more types of biomass can be used. Insome embodiments, the biomass feedstock comprises both a lignocellulosiccomponent (such as one described above) in addition to asucrose-containing component (e.g., sugarcane or energy cane) and/or astarch component (e.g., corn, wheat, rice, etc.). Various moisturelevels may be associated with the starting biomass. The biomassfeedstock need not be, but may be, relatively dry. In general, thebiomass is in the form of a particulate or chip, but particle size isnot critical in this invention.

Some variations provide a process for producing a hydrophobic cellulosematerial, the process comprising:

-   -   (a) providing a lignocellulosic biomass feedstock;    -   (b) fractionating the feedstock in the presence of an acid, a        solvent for lignin, and water, to generate cellulose-rich solids        and a liquid containing hemicellulose and lignin, wherein a        portion of the lignin deposits onto a surface of the        cellulose-rich solids, thereby rendering the cellulose-rich        solids at least partially hydrophobic;    -   (c) optionally mechanically treating the cellulose-rich solids        to form cellulose fibrils and/or cellulose crystals, having a        crystallinity of at least 60%; and    -   (d) recovering the hydrophobic cellulose material.

In some embodiments, the acid is selected from the group consisting ofsulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid,lignosulfonic acid, and combinations thereof.

The crystallinity of the hydrophobic cellulose material may at least 70%or at least 80%. The hydrophobic cellulose material may be characterizedby an average degree of polymerization from about 100 to about 1500,such as about 300 to about 700 or about 150 to about 250.

Optionally, the process further comprises chemically modifying thelignin to increase hydrophobicity of the hydrophobic cellulose material.Such modification to lignin could be done in solution or after thelignin is deposited onto cellulose.

Variations provide a process for producing a cellulose-containingproduct, the process comprising providing a lignin-coated cellulosematerial or a hydrophobic cellulose material, and then incorporating atleast a portion of the lignin-coated cellulose material or thehydrophobic cellulose material into a cellulose-containing product.

In some embodiments, the process comprises forming a structural objectthat includes the cellulose material, or a derivative thereof. Incertain embodiments, the process comprises forming a foam or aerogelthat includes the cellulose material, or a derivative thereof.

In some embodiments, the process comprises combining the cellulosematerial, or a derivative thereof, with one or more other materials toform a composite. The one or more other materials may include a polymerselected from polyolefins, polyesters, polyurethanes, polyamides, orcombinations thereof. The one or more other materials may includecarbon.

In some embodiments, the process comprises forming a film (such as aflexible film) comprising the cellulose material, or a derivativethereof. In some embodiments, the process comprises forming a coating orcoating precursor comprising the cellulose material, or a derivativethereof.

In some embodiments, the cellulose-containing product is configuredelectrochemically for carrying or storing an electrical current orvoltage.

In some embodiments, the cellulose-containing product is incorporatedinto a filter, membrane, or other separation device.

In some embodiments, the cellulose-containing product is incorporated asan additive into a coating, paint, or adhesive.

In some embodiments, the cellulose-containing product is configured as acatalyst, catalyst substrate, or co-catalyst.

In some embodiments, the cellulose-containing product is incorporated asa cement additive.

In some embodiments, the cellulose-containing product is a papercoating.

In some embodiments, the cellulose-containing product is incorporated asa thickening agent or rheological modifier.

In some embodiments, the cellulose-containing product is incorporated asan additive in a drilling fluid, such as an oil recovery fluid and/or agas recovery fluid.

A hydrophobic cellulose composition is disclosed with a cellulosecrystallinity of about 70% or greater, wherein the hydrophobic cellulosecomposition contains cellulose particles having a surface concentrationof lignin that is greater than a bulk concentration of lignin.

In some embodiments, the cellulose crystallinity is about 75% orgreater, such as about 80% or 80% or greater.

In some embodiments, the hydrophobic cellulose composition furthercomprises sulfur. The sulfur may be derived from the process to producethe hydrophobic cellulose, or otherwise incorporated into thecomposition.

In some embodiments, the hydrophobic cellulose composition ischaracterized by an average cellulose degree of polymerization fromabout 100 to about 1500, such as about 300 to about 700 or about 150 toabout 250. The composition may be characterized by a cellulose degree ofpolymerization distribution having a single peak or two peaks, forexample.

In various embodiments, the cellulose-containing product is selectedfrom the group consisting of a structural object, a foam, an aerogel, apolymer composite, a carbon composite, a film, a coating, a coatingprecursor, a current or voltage carrier, a filter, a membrane, acatalyst, a catalyst substrate, a coating additive, a paint additive, anadhesive additive, a cement additive, a paper coating, a thickeningagent, a rheological modifier, an additive for a drilling fluid, andcombinations or derivatives thereof.

In some embodiments, the cellulose-rich solids are treated with a totalmechanical energy of less than about 1000 kilowatt-hours per ton of thecellulose-rich solids, such as less than about 950, 900, 850, 800, 750,700, 650, 600, 550, 500, 450, 400, 350, 300, or 250 kilowatt-hours perton of the cellulose-rich solids. In certain embodiments, the totalmechanical energy is from about 100 kilowatt-hours to about 400kilowatt-hours per ton of the cellulose-rich solids. Energy consumptionmay be measured in any other suitable units. An ammeter measuringcurrent drawn by a motor driving the mechanical treatment device is oneway to obtain an estimate of the total mechanical energy.

Mechanically treating (when conducted) may employ one or more knowntechniques such as, but by no means limited to, milling, grinding,beating, sonicating, or any other means to form or release fibrilsand/or crystals in the cellulose. Essentially, any type of mill ordevice that physically separates fibers may be utilized. Such mills arewell-known in the industry and include, without limitation, Valleybeaters, single disk refiners, double disk refiners, conical refiners,including both wide angle and narrow angle, cylindrical refiners,homogenizers, microfluidizers, and other similar milling or grindingapparatus. See, for example, Smook, Handbook for Pulp & PaperTechnologists, Tappi Press, 1992.

The extent of mechanical treatment may be monitored during the processby any of several means. Certain optical instruments can providecontinuous data relating to the fiber length distributions and % fines,either of which may be used to define endpoints for the mechanicaltreatment step. The time, temperature, and pressure may vary duringmechanical treatment. For example, in some embodiments, sonication for atime from about 5 minutes to 2 hours, at ambient temperature andpressure, may be utilized.

Following mechanical treatment, the cellulose material may be classifiedby particle size. A portion of material may be subjected to a separateprocess, such as enzymatic hydrolysis to produce glucose. Such materialmay have good crystallinity, for example, but may not have desirableparticle size or degree of polymerization.

Some embodiments may further comprise treatment of the cellulose-richsolids with one or more enzymes or with one or more acids. When acidsare employed, they may be selected from the group consisting of sulfurdioxide, sulfurous acid, lignosulfonic acid, acetic acid, formic acid,and combinations thereof. Acids associated with hemicellulose, such asacetic acid or uronic acids, may be employed, alone or in conjunctionwith other acids. Also, the process may include treatment of thecellulose-rich solids with heat.

When an acid is employed, the acid may be a strong acid such as sulfuricacid, nitric acid, or phosphoric acid, for example. Weaker acids may beemployed, under more severe temperature and/or time. Enzymes thathydrolyze cellulose (i.e., cellulases) and possibly hemicellulose (i.e.,with hemicellulase activity) may be employed in step (c), either insteadof acids, or potentially in a sequential configuration before or afteracidic hydrolysis.

In some embodiments, the process comprises enzymatically treating thecellulose-rich solids to hydrolyze amorphous cellulose. In otherembodiments, or sequentially prior to or after enzymatic treatment, theprocess may comprise acid-treating the cellulose-rich solids tohydrolyze amorphous cellulose.

In some embodiments, the process further comprises enzymaticallytreating the crystalline cellulose. In other embodiments, orsequentially prior to or after enzymatic treatment, the process furthercomprises acid-treating treating the crystalline cellulose.

If desired, an enzymatic treatment may be employed prior to, or possiblysimultaneously with, mechanical treatment. However, in preferredembodiments, no enzyme treatment is necessary to hydrolyze amorphouscellulose or weaken the structure of the fiber walls before isolation offibers.

In some embodiments, the crystallinity of the cellulose-rich solids isat least 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%,72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%,86% or higher. In these or other embodiments, the crystallinity of thecellulose material is at least 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%,68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%,82%, 83%, 84%, 85%, 86% or higher. The crystallinity may be measuredusing any known techniques. For example, X-ray diffraction andsolid-state ¹³C nuclear magnetic resonance may be utilized.

In some embodiments, the cellulose material is characterized by anaverage degree of polymerization from about 100 to about 1500, such asabout 125, 150, 175, 200, 225, 250, 300, 400, 500, 600, 700, 800, 900,1000, 1100, 1200, 1300, or 1400. For example, the cellulose material maybe characterized by an average degree of polymerization from about 300to about 700, or from about 150 to about 250. The cellulose material,when in the form of crystals, may have a degree of polymerization lessthan 100, such as about 75, 50, 25, or 10. Portions of the material mayhave a degree of polymerization that is higher than 1500, such as about2000, 3000, 4000, or 5000.

In some embodiments, the cellulose material is characterized by a degreeof polymerization distribution having a single peak. In otherembodiments, the cellulose material is characterized by a degree ofpolymerization distribution having two peaks, such as one centered inthe range of 150-250 and another peak centered in the range of 300-700.

In some embodiments, the cellulose material is characterized by anaverage length-to-width aspect ratio of particles from about 10 to about1000, such as about 15, 20, 25, 35, 50, 75, 100, 150, 200, 250, 300,400, or 500. Fibrils are generally associated with higher aspect ratiosthan crystals. Nanocrystals, for example, may have a length range ofabout 100 nm to 500 nm and a diameter of about 4 nm, translating to anaspect ratio of 25 to 125. Nanofibrils may have a length of about 2000nm and diameter range of 5 to 50 nm, translating to an aspect ratio of40 to 400. In some embodiments, the aspect ratio is less than 50, lessthan 45, less than 40, less than 35, less than 30, less than 25, lessthan 20, less than 15, or less than 10.

Optionally, the process further comprises hydrolyzing amorphouscellulose into glucose in, and fermenting the glucose to a fermentationproduct. Optionally, the process further comprises recovering,fermenting, or further treating hemicellulosic sugars derived from thehemicellulose. Optionally, the process further comprises recovering,combusting, or further treating the lignin (i.e., the lignin that didnot deposit onto the cellulose).

Glucose that is generated from hydrolysis of amorphous cellulose may beintegrated into an overall process to produce ethanol, or anotherfermentation co-product. Thus in some embodiments, the process furthercomprises hydrolyzing amorphous cellulose into glucose, and recoveringthe glucose. The glucose may be purified and sold. Or the glucose may befermented to a fermentation product, such as but not limited to ethanol.The glucose or a fermentation product may be recycled to the front end,such as to hemicellulose sugar processing, if desired.

When hemicellulosic sugars are recovered and fermented, they may befermented to produce a monomer or precursor thereof. The monomer may bepolymerized to produce a polymer, which may then be combined with thecellulose material to form a polymer-cellulose composite.

In some embodiments, the process further comprises chemically convertingthe cellulose material to one or more cellulose derivatives. Forexample, cellulose derivatives may be selected from the group consistingof esters, ethers, ether esters, alkylated compounds, cross-linkedcompounds, acid-functionalized compounds, base-functionalized compounds,and combinations thereof.

Various types of cellulose functionalization or derivatization may beemployed, such as functionalization using polymers, chemical surfacemodification, functionalization using nanoparticles, modification withinorganics or surfactants, or biochemical modification.

In some embodiments, the SO₂ concentration is from about 12 wt % toabout 30 wt %. In some embodiments, the fractionation temperature isfrom about 140° C. to about 170° C. In some embodiments, thefractionation time is from about 1 hour to about 2 hours. The process iscontrolled such that a portion of the solubilized lignin (or anothersource of lignin) intentionally deposits back onto a surface of thecellulose-rich solids, thereby rendering the cellulose-rich solids atleast partially hydrophobic.

A significant factor limiting the application of strength-enhancing,lightweight cellulose in composites is cellulose's inherenthydrophilicity. Surface modification of the cellulose surface to imparthydrophobicity to enable uniform dispersion in a hydrophobic polymermatrix is an active area of study. It has been discovered that whenpreparing cellulose using the processes described herein, lignin maycondense on pulp under certain conditions, giving a rise in Kappa numberand production of a brown or black material. The lignin increases thehydrophobicity of the cellulose precursor material, and thathydrophobicity is retained provided that there is not removal of thelignin through bleaching or other steps. (Some bleaching may still beperformed, either to adjust lignin content or to attack a certain typeof lignin, for example.)

Process conditions may be varied to accomplish the desire degree oflignin deposition. Conditions which tend to promote lignin depositiononto fibers are extended time and/or temperature, reduced pH, andreduced concentration of solvent for lignin (e.g., about 40 wt %, 35 wt%, 30 wt %, 25 wt %, 20 wt %, or less ethanol). Alternatively, oradditionally, the process may include one or more washing steps that areadapted to deposit at least some of the lignin that was solubilizedduring the initial fractionation. One approach is to wash with waterrather than a solution of water and solvent. Because lignin is generallynot soluble in water, it will begin to precipitate. Optionally, otherconditions may be varied, such as pH and temperature, duringfractionation, washing, or other steps, to optimize the amount of lignindeposited on surfaces. It is noted that in order for the lignin surfaceconcentration to be higher than the bulk concentration, the lignin needsto be first pulled into solution and then redeposited; internal lignin(within particles of cellulose) does not enhance hydrophobicity in thesame way.

Optionally, the process for producing a hydrophobic cellulose materialmay further include chemically modifying the lignin to increasehydrophobicity of the cellulose material. The chemical modification oflignin may be conducted during fractionation, during deposition,following deposition, or some combination thereof.

High loading rates of lignin have been achieved in thermoplastics. Evenhigher loading levels are obtained with well-known modifications oflignin. The preparation of useful polymeric materials containing asubstantial amount of lignin has been the subject of investigations formore than thirty years. Typically, lignin may be blended intopolyolefins or polyesters by extrusion up to 25-40 wt % while satisfyingmechanical characteristics. In order to increase the compatibilitybetween lignin and other hydrophobic polymers, different approaches havebeen used. For example, chemical modification of lignin may beaccomplished through esterification with long-chain fatty acids.

Any known chemical modifications may be carried out on the lignin, tofurther increase the hydrophobic nature of the lignin-coated cellulosematerial provided by embodiments of this invention.

The cellulose material may further contain some sulfonated lignin thatis derived from sulfonation reactions with SO₂ (when used as the acid infractionation) during the biomass digestion. The amount of sulfonatedlignin may be about 0.1 wt % (or less), 0.2 wt %, 0.5 wt %, 0.8 wt %, 1wt %, or more. Also, without being limited by any theory, it isspeculated that a small amount of sulfur may chemically react withcellulose itself, in some embodiments.

A cellulose-containing product may include any of the disclosedhydrophobic, lignin-coated cellulose compositions. Manycellulose-containing products are possible. For example, acellulose-containing product may be selected from the group consistingof a structural object, a foam, an aerogel, a polymer composite, acarbon composite, a film, a coating, a coating precursor, a current orvoltage carrier, a filter, a membrane, a catalyst, a catalyst substrate,a coating additive, a paint additive, an adhesive additive, a cementadditive, a paper coating, a thickening agent, a rheological modifier,an additive for a drilling fluid, and combinations or derivativesthereof.

In some embodiments, the cellulose-containing product is amoisture-barrier pressed pulp product. In numerous applicationsincluding packaging, moisture may be present. In a moisture contentsituation, a moisture barrier is desirable to prevent, or at least slow,the leakage of any moisture. Currently, a pulp product may be treated toproduce an end product having a moisture barrier. Conventional methodsof creating moisture barrier products include coating linerboard with apolymeric water-repellant laminate, or coating linerboard with wax or awax-like substance. However, each of these methods adds significantproduction costs to the fabrication process. Beyond production costs,these processes produce a resultant moisture barrier product that is notcompletely repulpable and, in fact, is often rejected by recyclingplants only to end up in a landfill. Moreover, the resultant moisturebarrier product has a surface coating that can affect production. Forinstance, the surface coating is often difficult to print on therebyrequiring a special ink. The surface coating may also create problems ingluing portions of the corrugated to form a container, the glue notadhering well to the surface coating. The surface coating is easilyscratched reducing the effectiveness of the moisture barrier protection.

In some embodiments of the invention, a moisture-barrier pulp product isprovided by lignin-coated, hydrophobic material. The moisture-barrierpulp product may be incorporated into a variety of final products andgeometries, including coatings, structural objects (e.g., containers),and so on. In some embodiments, the moisture-barrier pulp product is amoisture-barrier pressed pulp product. In some embodiments, themoisture-barrier pulp product is a moisture-barrier molded pulp product.In some embodiments, the moisture-barrier pulp product is amoisture-barrier extruded pulp product.

Some process variations may be understood with reference to FIGS. 1-4.Dotted lines denote optional streams. Various embodiments will now befurther described, without limitation as to the scope of the invention.These embodiments are exemplary in nature.

In some embodiments, a first process step is “cooking” (equivalently,“digesting”) which fractionates the three lignocellulosic materialcomponents (cellulose, hemicellulose, and lignin) to allow easydownstream removal. Specifically, hemicelluloses are dissolved and over50% are completely hydrolyzed; cellulose is separated but remainsresistant to hydrolysis; and part of the lignin is sulfonated intowater-soluble lignosulfonates.

The lignocellulosic material is processed in a solution (cooking liquor)of aliphatic alcohol, water, and sulfur dioxide. The cooking liquorpreferably contains at least 10 wt %, such as at least 20 wt %, 30 wt %,40 wt %, or 50 wt % of a solvent for lignin. For example, the cookingliquor may contain about 30-70 wt % solvent, such as about 50 wt %solvent. The solvent for lignin may be an aliphatic alcohol, such asmethanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol,isobutanol, 1-pentanol, 1-hexanol, or cyclohexanol. The solvent forlignin may be an aromatic alcohol, such as phenol or cresol. Otherlignin solvents are possible, such as (but not limited to) glycerol,methyl ethyl ketone, or diethyl ether. Combinations of more than onesolvent may be employed.

Preferably, enough solvent is included in the extractant mixture todissolve the lignin present in the starting material. The solvent forlignin may be completely miscible, partially miscible, or immisciblewith water, so that there may be more than one liquid phase. Potentialprocess advantages arise when the solvent is miscible with water, andalso when the solvent is immiscible with water. When the solvent iswater-miscible, a single liquid phase forms, so mass transfer of ligninand hemicellulose extraction is enhanced, and the downstream processmust only deal with one liquid stream. When the solvent is immiscible inwater, the extractant mixture readily separates to form liquid phases,so a distinct separation step can be avoided or simplified. This can beadvantageous if one liquid phase contains most of the lignin and theother contains most of the hemicellulose sugars, as this facilitatesrecovering the lignin from the hemicellulose sugars.

The cooking liquor preferably contains sulfur dioxide and/or sulfurousacid (H₂SO₃). The cooking liquor preferably contains SO₂, in dissolvedor reacted form, in a concentration of at least 3 wt %, preferably atleast 6 wt %, more preferably at least 8 wt %, such as about 9 wt %, 10wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 20 wt %, 25 wt %, 30wt % or higher. The cooking liquor may also contain one or more species,separately from SO₂, to adjust the pH. The pH of the cooking liquor istypically about 4 or less.

Sulfur dioxide is a preferred acid catalyst, because it can be recoveredeasily from solution after hydrolysis. The majority of the SO₂ from thehydrolysate may be stripped and recycled back to the reactor. Recoveryand recycling translates to less lime required compared toneutralization of comparable sulfuric acid, less solids to dispose of,and less separation equipment. The increased efficiency owing to theinherent properties of sulfur dioxide mean that less total acid or othercatalysts may be required. This has cost advantages, since sulfuric acidcan be expensive. Additionally, and quite significantly, less acid usagealso will translate into lower costs for a base (e.g., lime) to increasethe pH following hydrolysis, for downstream operations. Furthermore,less acid and less base will also mean substantially less generation ofwaste salts (e.g., gypsum) that may otherwise require disposal.

In some embodiments, an additive may be included in amounts of about 0.1wt % to 10 wt % or more to increase cellulose viscosity. Exemplaryadditives include ammonia, ammonia hydroxide, urea, anthraquinone,magnesium oxide, magnesium hydroxide, sodium hydroxide, and theirderivatives.

The cooking is performed in one or more stages using batch or continuousdigestors. Solid and liquid may flow cocurrently or countercurrently, orin any other flow pattern that achieves the desired fractionation. Thecooking reactor may be internally agitated, if desired.

Depending on the lignocellulosic material to be processed, the cookingconditions are varied, with temperatures from about 65° C. to 190° C.,for example 75° C., 85° C., 95° C., 105° C., 115° C., 125° C., 130° C.,135° C., 140° C., 145° C., 150° C., 155° C., 165° C. or 170° C., andcorresponding pressures from about 1 atmosphere to about 15 atmospheresin the liquid or vapor phase. The cooking time of one or more stages maybe selected from about 15 minutes to about 720 minutes, such as about30, 45, 60, 90, 120, 140, 160, 180, 250, 300, 360, 450, 550, 600, or 700minutes. Generally, there is an inverse relationship between thetemperature used during the digestion step and the time needed to obtaingood fractionation of the biomass into its constituent parts.

The cooking liquor to lignocellulosic material ratio may be selectedfrom about 1 to about 10, such as about 2, 3, 4, 5, or 6. In someembodiments, biomass is digested in a pressurized vessel with low liquorvolume (low ratio of cooking liquor to lignocellulosic material), sothat the cooking space is filled with ethanol and sulfur dioxide vaporin equilibrium with moisture. The cooked biomass is washed inalcohol-rich solution to recover lignin and dissolved hemicelluloses,while the remaining pulp is further processed. In some embodiments, theprocess of fractionating lignocellulosic material comprises vapor-phasecooking of lignocellulosic material with aliphatic alcohol (or othersolvent for lignin), water, and sulfur dioxide. See, for example, U.S.Pat. Nos. 8,038,842 and 8,268,125 which are incorporated by referenceherein.

A portion or all of the sulfur dioxide may be present as sulfurous acidin the extract liquor. In certain embodiments, sulfur dioxide isgenerated in situ by introducing sulfurous acid, sulfite ions, bisulfiteions, combinations thereof, or a salt of any of the foregoing. Excesssulfur dioxide, following hydrolysis, may be recovered and reused. Insome embodiments, sulfur dioxide is saturated in water (or aqueoussolution, optionally with an alcohol) at a first temperature, and thehydrolysis is then carried out at a second, generally higher,temperature. In some embodiments, sulfur dioxide is sub-saturated. Insome embodiments, sulfur dioxide is super-saturated. In someembodiments, sulfur dioxide concentration is selected to achieve acertain degree of lignin sulfonation, such as 1%, 2%, 3%, 4%, 5%, 6%,7%, 8%, 9%, or 10% sulfur content. SO₂ reacts chemically with lignin toform stable lignosulfonic acids which may be present both in the solidand liquid phases.

The concentration of sulfur dioxide, additives, and aliphatic alcohol(or other solvent) in the solution and the time of cook may be varied tocontrol the yield of cellulose and hemicellulose in the pulp. Theconcentration of sulfur dioxide and the time of cook may be varied tocontrol the yield of lignin versus lignosulfonates in the hydrolysate.In some embodiments, the concentration of sulfur dioxide, temperature,and the time of cook may be varied to control the yield of fermentablesugars.

Once the desired amount of fractionation of both hemicellulose andlignin from the solid phase is achieved, the liquid and solid phases areseparated. Conditions for the separation may be selected to minimize orenhance the reprecipitation of the extracted lignin on the solid phase.Minimizing lignin reprecipitation is favored by conducting separation orwashing at a temperature of at least the glass-transition temperature oflignin (about 120° C.); conversely, enhancing lignin reprecipitation isfavored by conducting separation or washing at a temperature less thanthe glass-transition temperature of lignin.

The physical separation can be accomplished either by transferring theentire mixture to a device that can carry out the separation andwashing, or by removing only one of the phases from the reactor whilekeeping the other phase in place. The solid phase can be physicallyretained by appropriately sized screens through which liquid can pass.The solid is retained on the screens and can be kept there forsuccessive solid-wash cycles. Alternately, the liquid may be retainedand solid phase forced out of the reaction zone, with centrifugal orother forces that can effectively transfer the solids out of the slurry.In a continuous system, countercurrent flow of solids and liquid canaccomplish the physical separation.

The recovered solids normally will contain a quantity of lignin andsugars, some of which can be removed easily by washing. Thewashing-liquid composition can be the same as or different than theliquor composition used during fractionation. Multiple washes may beperformed to increase effectiveness. Preferably, one or more washes areperformed with a composition including a solvent for lignin, to removeadditional lignin from the solids, followed by one or more washes withwater to displace residual solvent and sugars from the solids. Recyclestreams, such as from solvent-recovery operations, may be used to washthe solids.

After separation and washing as described, a solid phase and at leastone liquid phase are obtained. The solid phase contains substantiallyundigested cellulose. A single liquid phase is usually obtained when thesolvent and the water are miscible in the relative proportions that arepresent. In that case, the liquid phase contains, in dissolved form,most of the lignin originally in the starting lignocellulosic material,as well as soluble monomeric and oligomeric sugars formed in thehydrolysis of any hemicellulose that may have been present. Multipleliquid phases tend to form when the solvent and water are wholly orpartially immiscible. The lignin tends to be contained in the liquidphase that contains most of the solvent. Hemicellulose hydrolysisproducts tend to be present in the liquid phase that contains most ofthe water.

In some embodiments, hydrolysate from the cooking step is subjected topressure reduction. Pressure reduction may be done at the end of a cookin a batch digestor, or in an external flash tank after extraction froma continuous digestor, for example. The flash vapor from the pressurereduction may be collected into a cooking liquor make-up vessel. Theflash vapor contains substantially all the unreacted sulfur dioxidewhich may be directly dissolved into new cooking liquor. The celluloseis then removed to be washed and further treated as desired.

A process washing step recovers the hydrolysate from the cellulose. Thewashed cellulose is pulp that may be used for various purposes (e.g.,paper or nanocellulose production). The weak hydrolysate from the washercontinues to the final reaction step; in a continuous digestor this weakhydrolysate may be combined with the extracted hydrolysate from theexternal flash tank. In some embodiments, washing and/or separation ofhydrolysate and cellulose-rich solids is conducted at a temperature ofat least about 100° C., 110° C., or 120° C. The washed cellulose mayalso be used for glucose production via cellulose hydrolysis withenzymes or acids.

In another reaction step, the hydrolysate may be further treated in oneor multiple steps to hydrolyze the oligomers into monomers. This stepmay be conducted before, during, or after the removal of solvent andsulfur dioxide. The solution may or may not contain residual solvent(e.g. alcohol). In some embodiments, sulfur dioxide is added or allowedto pass through to this step, to assist hydrolysis. In these or otherembodiments, an acid such as sulfurous acid or sulfuric acid isintroduced to assist with hydrolysis. In some embodiments, thehydrolysate is autohydrolyzed by heating under pressure. In someembodiments, no additional acid is introduced, but lignosulfonic acidsproduced during the initial cooking are effective to catalyze hydrolysisof hemicellulose oligomers to monomers. In various embodiments, thisstep utilizes sulfur dioxide, sulfurous acid, sulfuric acid at aconcentration of about 0.01 wt % to 30 wt %, such as about 0.05 wt %,0.1 wt %, 0.2 wt %, 0.5 wt %, 1 wt %, 2 wt %, 5 wt %, 10 wt %, or 20 wt%. This step may be carried out at a temperature from about 100° C. to220° C., such as about 110° C., 120° C., 130° C., 140° C., 150° C., 160°C., 170° C., 180° C., 190° C., 200° C., or 210° C. Heating may be director indirect to reach the selected temperature.

The reaction step produces fermentable sugars which can then beconcentrated by evaporation to a fermentation feedstock. Concentrationby evaporation may be accomplished before, during, or after thetreatment to hydrolyze oligomers. The final reaction step may optionallybe followed by steam stripping of the resulting hydrolysate to removeand recover sulfur dioxide and alcohol, and for removal of potentialfermentation-inhibiting side products. The evaporation process may beunder vacuum or pressure, from about −0.1 atmospheres to about 10atmospheres, such as about 0.1 atm, 0.3 atm, 0.5 atm, 1.0 atm, 1.5 atm,2 atm, 4 atm, 6 atm, or 8 atm.

Recovering and recycling the sulfur dioxide may utilize separations suchas, but not limited to, vapor-liquid disengagement (e.g. flashing),steam stripping, extraction, or combinations or multiple stages thereof.Various recycle ratios may be practiced, such as about 0.1, 0.2, 0.3,0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, or more. In some embodiments, about90-99% of initially charged SO₂ is readily recovered by distillationfrom the liquid phase, with the remaining 1-10% (e.g., about 3-5%) ofthe SO₂ primarily bound to dissolved lignin in the form oflignosulfonates.

In a preferred embodiment, the evaporation step utilizes an integratedalcohol stripper and evaporator. Evaporated vapor streams may besegregated so as to have different concentrations of organic compoundsin different streams. Evaporator condensate streams may be segregated soas to have different concentrations of organic compounds in differentstreams. Alcohol may be recovered from the evaporation process bycondensing the exhaust vapor and returning to the cooking liquor make-upvessel in the cooking step. Clean condensate from the evaporationprocess may be used in the washing step.

In some embodiments, an integrated alcohol stripper and evaporatorsystem is employed, wherein aliphatic alcohol is removed by vaporstripping, the resulting stripper product stream is concentrated byevaporating water from the stream, and evaporated vapor is compressedusing vapor compression and is reused to provide thermal energy.

The hydrolysate from the evaporation and final reaction step containsmainly fermentable sugars but may also contain lignin depending on thelocation of lignin separation in the overall process configuration. Thehydrolysate may be concentrated to a concentration of about 5 wt % toabout 60 wt % solids, such as about 10 wt %, 15 wt %, 20 wt %, 25 wt %,30 wt %, 35 wt %, 40 wt %, 45 wt %, 50 wt % or 55 wt % solids. Thehydrolysate contains fermentable sugars.

Fermentable sugars are defined as hydrolysis products of cellulose,galactoglucomannan, glucomannan, arabinoglucuronoxylans,arabinogalactan, and glucuronoxylans into their respective short-chainedoligomers and monomer products, i.e., glucose, mannose, galactose,xylose, and arabinose. The fermentable sugars may be recovered inpurified form, as a sugar slurry or dry sugar solids, for example. Anyknown technique may be employed to recover a slurry of sugars or to drythe solution to produce dry sugar solids.

In some embodiments, the fermentable sugars are fermented to producebiochemicals or biofuels such as (but by no means limited to) ethanol,isopropanol, acetone, 1-butanol, isobutanol, lactic acid, succinic acid,or any other fermentation products. Some amount of the fermentationproduct may be a microorganism or enzymes, which may be recovered ifdesired.

When the fermentation will employ bacteria, such as Clostridia bacteria,it is preferable to further process and condition the hydrolysate toraise pH and remove residual SO₂ and other fermentation inhibitors. Theresidual SO₂ (i.e., following removal of most of it by stripping) may becatalytically oxidized to convert residual sulfite ions to sulfate ionsby oxidation. This oxidation may be accomplished by adding an oxidationcatalyst, such as FeSO4.7H₂O, that oxidizes sulfite ions to sulfateions. Preferably, the residual SO₂ is reduced to less than about 100ppm, 50 ppm, 25 ppm, 10 ppm, 5 ppm, or 1 ppm.

In some embodiments, the process further comprises recovering the ligninas a co-product. The sulfonated lignin may also be recovered as aco-product. In certain embodiments, the process further comprisescombusting or gasifying the sulfonated lignin, recovering sulfurcontained in the sulfonated lignin in a gas stream comprising reclaimedsulfur dioxide, and then recycling the reclaimed sulfur dioxide forreuse.

The process lignin separation step is for the separation of lignin fromthe hydrolysate and can be located before or after the final reactionstep and evaporation. If located after, then lignin will precipitatefrom the hydrolysate since alcohol has been removed in the evaporationstep. The remaining water-soluble lignosulfonates may be precipitated byconverting the hydrolysate to an alkaline condition (pH higher than 7)using, for example, an alkaline earth oxide, preferably calcium oxide(lime). The combined lignin and lignosulfonate precipitate may befiltered. The lignin and lignosulfonate filter cake may be dried as aco-product or burned or gasified for energy production. The hydrolysatefrom filtering may be recovered and sold as a concentrated sugarsolution product or further processed in a subsequent fermentation orother reaction step.

Native (non-sulfonated) lignin is hydrophobic, while lignosulfonates arehydrophilic. Hydrophilic lignosulfonates may have less propensity toclump, agglomerate, and stick to surfaces. Even lignosulfonates that doundergo some condensation and increase of molecular weight, will stillhave an HSO₃ group that will contribute some solubility (hydrophilic).

In some embodiments, the soluble lignin precipitates from thehydrolysate after solvent has been removed in the evaporation step. Insome embodiments, reactive lignosulfonates are selectively precipitatedfrom hydrolysate using excess lime (or other base, such as ammonia) inthe presence of aliphatic alcohol. In some embodiments, hydrated lime isused to precipitate lignosulfonates. In some embodiments, part of thelignin is precipitated in reactive form and the remaining lignin issulfonated in water-soluble form.

The process fermentation and distillation steps are intended for theproduction of fermentation products, such as alcohols or organic acids.After removal of cooking chemicals and lignin, and further treatment(oligomer hydrolysis), the hydrolysate contains mainly fermentablesugars in water solution from which any fermentation inhibitors havebeen preferably removed or neutralized. The hydrolysate is fermented toproduce dilute alcohol or organic acids, from 1 wt % to 20 wt %concentration. The dilute product is distilled or otherwise purified asis known in the art.

When alcohol is produced, such as ethanol, some of it may be used forcooking liquor makeup in the process cooking step. Also, in someembodiments, a distillation column stream, such as the bottoms, with orwithout evaporator condensate, may be reused to wash cellulose. In someembodiments, lime may be used to dehydrate product alcohol. Sideproducts may be removed and recovered from the hydrolysate. These sideproducts may be isolated by processing the vent from the final reactionstep and/or the condensate from the evaporation step. Side productsinclude furfural, hydroxymethyl furfural (HMF), methanol, acetic acid,and lignin-derived compounds, for example.

The glucose may be fermented to an alcohol, an organic acid, or anotherfermentation product. The glucose may be used as a sweetener orisomerized to enrich its fructose content. The glucose may be used toproduce baker's yeast. The glucose may be catalytically or thermallyconverted to various organic acids and other materials.

When hemicellulose is present in the starting biomass, all or a portionof the liquid phase contains hemicellulose sugars and soluble oligomers.It is preferred to remove most of the lignin from the liquid, asdescribed above, to produce a fermentation broth which will containwater, possibly some of the solvent for lignin, hemicellulose sugars,and various minor components from the digestion process. Thisfermentation broth can be used directly, combined with one or more otherfermentation streams, or further treated. Further treatment can includesugar concentration by evaporation; addition of glucose or other sugars(optionally as obtained from cellulose saccharification); addition ofvarious nutrients such as salts, vitamins, or trace elements; pHadjustment; and removal of fermentation inhibitors such as acetic acidand phenolic compounds. The choice of conditioning steps should bespecific to the target product(s) and microorganism(s) employed.

In some embodiments, hemicellulose sugars are not fermented but ratherare recovered and purified, stored, sold, or converted to a specialtyproduct. Xylose, for example, can be converted into xylitol.

A lignin product can be readily obtained from a liquid phase using oneor more of several methods. One simple technique is to evaporate off allliquid, resulting in a solid lignin-rich residue. This technique wouldbe especially advantageous if the solvent for lignin iswater-immiscible. Another method is to cause the lignin to precipitateout of solution. Some of the ways to precipitate the lignin include (1)removing the solvent for lignin from the liquid phase, but not thewater, such as by selectively evaporating the solvent from the liquidphase until the lignin is no longer soluble; (2) diluting the liquidphase with water until the lignin is no longer soluble; and (3)adjusting the temperature and/or pH of the liquid phase. Methods such ascentrifugation can then be utilized to capture the lignin. Yet anothertechnique for removing the lignin is continuous liquid-liquid extractionto selectively remove the lignin from the liquid phase, followed byremoval of the extraction solvent to recover relatively pure lignin.

Lignin produced in accordance with the invention can be used as a fuel.As a solid fuel, lignin is similar in energy content to coal. Lignin canact as an oxygenated component in liquid fuels, to enhance octane whilemeeting standards as a renewable fuel. The lignin produced herein canalso be used as polymeric material, and as a chemical precursor forproducing lignin derivatives. The sulfonated lignin may be sold as alignosulfonate product, or burned for fuel value.

The present invention also provides systems configured for carrying outthe disclosed processes, and compositions produced therefrom. Any streamgenerated by the disclosed processes may be partially or completedrecovered, purified or further treated, and/or marketed or sold.

Certain cellulose-containing products provide high transparency, goodmechanical strength, and/or enhanced gas (e.g., O₂ or CO₂) barrierproperties, for example. Certain cellulose-containing productscontaining hydrophobic cellulose materials provided herein may be usefulas anti-wetting and anti-icing coatings, for example.

Some embodiments provide cellulose-containing products with applicationsfor sensors, catalysts, antimicrobial materials, current carrying andenergy storage capabilities. Cellulose crystals have the capacity toassist in the synthesis of metallic and semiconducting nanoparticlechains.

Some embodiments provide composites containing cellulose and acarbon-containing material, such as (but not limited to) lignin,graphite, graphene, or carbon aerogels.

Cellulose may be coupled with the stabilizing properties of surfactantsand exploited for the fabrication of nanoarchitectures of varioussemiconducting materials.

The reactive surface of —OH side groups in cellulose facilitatesgrafting chemical species to achieve different surface properties.Surface functionalization allows the tailoring of particle surfacechemistry to facilitate self-assembly, controlled dispersion within awide range of matrix polymers, and control of both the particle-particleand particle-matrix bond strength. Composites may be transparent, havetensile strengths greater than cast iron, and have very low coefficientof thermal expansion. Potential applications include, but are notlimited to, barrier films, antimicrobial films, transparent films,flexible displays, reinforcing fillers for polymers, biomedicalimplants, pharmaceuticals, drug delivery, fibers and textiles, templatesfor electronic components, separation membranes, batteries,supercapacitors, electroactive polymers, and many others.

Other cellulose applications suitable to the present invention includereinforced polymers, high-strength spun fibers and textiles, advancedcomposite materials, films for barrier and other properties, additivesfor coatings, paints, lacquers and adhesives, switchable opticaldevices, pharmaceuticals and drug delivery systems, bone replacement andtooth repair, improved paper, packaging and building products, additivesfor foods and cosmetics, catalysts, and hydrogels.

Aerospace and transportation composites may benefit from highcrystallinity. Automotive applications include cellulose composites withpolypropylene, polyamide (e.g. Nylons), or polyesters (e.g. PBT).

Cellulose materials provided herein are suitable as strength-enhancingadditives for renewable and biodegradable composites. The cellulosicfibrillar structures may function as a binder between two organic phasesfor improved fracture toughness and prevention of crack formation forapplication in packaging, construction materials, appliances, andrenewable fibers.

Cellulose materials provided herein are suitable as transparent anddimensional stable strength-enhancing additives and substrates forapplication in flexible displays, flexible circuits, printableelectronics, and flexible solar panels. Cellulose is incorporated intothe substrate-sheets are formed by vacuum filtration, dried underpressure and calandered, for example. In a sheet structure, celluloseacts as a glue between the filler aggregates. The formed calanderedsheets are smooth and flexible.

Cellulose materials provided herein are suitable for composite andcement additives allowing for crack reduction and increased toughnessand strength. Foamed, cellular cellulose-concrete hybrid materials allowfor lightweight structures with increased crack reduction and strength.

Strength enhancement with cellulose increases both the binding area andbinding strength for application in high strength, high bulk, highfiller content paper and board with enhanced moisture and oxygen barrierproperties.

Fibrillated cellulose nanopaper has a higher density and higher tensilemechanical properties than conventional paper. It can also be opticallytransparent and flexible, with low thermal expansion and excellentoxygen barrier characteristics. The functionality of the nanopaper canbe further broadened by incorporating other entities such as carbonnanotubes, nanoclay or a conductive polymer coating.

Porous cellulose may be used for cellular bioplastics, insulation andplastics and bioactive membranes and filters. Highly porous cellulosematerials are generally of high interest in the manufacturing offiltration media as well as for biomedical applications, e.g., indialysis membranes.

Cellulose materials provided herein are suitable as coating materials asthey are expected to have a high oxygen barrier and affinity to woodfibers for application in food packaging and printing papers.

Cellulose materials provided herein are suitable as additives to improvethe durability of paint, protecting paints and varnishes from attritioncaused by UV radiation.

Cellulose materials provided herein are suitable as thickening agents infood and cosmetics products. Cellulose can be used as thixotropic,biodegradable, dimensionally stable thickener (stable againsttemperature and salt addition). Cellulose materials provided herein aresuitable as a Pickering stabilizer for emulsions and particle stabilizedfoam.

The large surface area of these cellulose materials in combination withtheir biodegradability makes them attractive materials for highlyporous, mechanically stable aerogels. Cellulose aerogels display aporosity of 95% or higher, and they are ductile and flexible.

Drilling fluids are fluids used in drilling in the natural gas and oilindustries, as well as other industries that use large drillingequipment. The drilling fluids are used to lubricate, providehydrostatic pressure, and to keep the drill cool, and the hole as cleanas possible of drill cuttings. Cellulose materials provided herein aresuitable as additives to these drilling fluids.

In this detailed description, reference has been made to multipleembodiments of the invention and non-limiting examples relating to howthe invention can be understood and practiced. Other embodiments that donot provide all of the features and advantages set forth herein may beutilized, without departing from the spirit and scope of the presentinvention. This invention incorporates routine experimentation andoptimization of the methods and systems described herein. Suchmodifications and variations are considered to be within the scope ofthe invention defined by the claims.

All publications, patents, and patent applications cited in thisspecification are herein incorporated by reference in their entirety asif each publication, patent, or patent application were specifically andindividually put forth herein.

Where methods and steps described above indicate certain eventsoccurring in certain order, those of ordinary skill in the art willrecognize that the ordering of certain steps may be modified and thatsuch modifications are in accordance with the variations of theinvention. Additionally, certain of the steps may be performedconcurrently in a parallel process when possible, as well as performedsequentially.

Therefore, to the extent there are variations of the invention, whichare within the spirit of the disclosure or equivalent to the inventionsfound in the appended claims, it is the intent that this patent willcover those variations as well. The present invention shall only belimited by what is claimed.

What is claimed is:
 1. A process for producing a lignin-coated cellulose material, said process comprising: (a) providing a lignocellulosic biomass feedstock; (b) fractionating said feedstock in the presence of an acid, a solvent for lignin, and water, to generate cellulose-rich solids and a liquid containing hemicellulose and lignin, wherein said feedstock, said acid, said solvent for lignin, and said water are all contained together in a digestor; (c) depositing at least some of said lignin, from said liquid, onto a surface of said cellulose-rich solids to generate a lignin-coated cellulose material containing cellulose particles having a surface concentration of lignin that is greater than a bulk concentration of lignin; (d) mechanically treating said lignin-coated cellulose material with a total mechanical energy of less than about 1000 kilowatt-hours per ton of said lignin-coated cellulose material, wherein said mechanically treating releases cellulose fibrils and/or cellulose crystals; and (e) recovering said lignin-coated cellulose material, wherein cellulose crystallinity of said lignin-coated cellulose material is at least 60%, wherein said lignin-coated cellulose material is at least partially hydrophobic, and wherein said lignin-coated cellulose material is lignin-coated microfibrillated cellulose or lignin-coated microcrystalline cellulose.
 2. The process of claim 1, wherein said acid is selected from the group consisting of sulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid, lignosulfonic acid, and combinations thereof.
 3. The process of claim 2, wherein said acid is sulfur dioxide.
 4. The process of claim 3, wherein sulfur dioxide concentration in step (b) is from about 12 wt % to about 30 wt %.
 5. The process of claim 1, wherein fractionation temperature in step (b) is from about 140° C. to about 170° C.
 6. The process of claim 1, wherein fractionation time in step (b) is from about 1 hour to about 2 hours.
 7. The process of claim 1, wherein steps (c) and (d) are integrated.
 8. The process of claim 1, wherein said lignin-coated cellulose material is treated with a total mechanical energy of less than about 500 kilowatt-hours per ton of said lignin-coated cellulose material.
 9. The process of claim 1, wherein said process further comprises treatment of said lignin-coated cellulose material with one or more enzymes.
 10. The process of claim 1, wherein said process further comprises treatment of said lignin-coated cellulose material with one or more acids.
 11. The process of claim 10, wherein said one or more acids are selected from the group consisting of sulfur dioxide, sulfurous acid, lignosulfonic acid, acetic acid, formic acid, and combinations thereof.
 12. The process of claim 1, wherein said process further comprises treatment of said lignin-coated cellulose material with heat.
 13. The process of claim 1, wherein said cellulose crystallinity of said lignin-coated cellulose material is at least 70%.
 14. The process of claim 13, wherein said cellulose crystallinity of said lignin-coated cellulose material is at least 80%.
 15. The process of claim 1, said process further comprising chemically converting said lignin-coated cellulose material to one or more lignin-coated cellulose derivatives.
 16. The process of claim 15, wherein said lignin-coated cellulose derivatives are selected from the group consisting of cellulose esters, cellulose ethers, cellulose ether esters, alkylated cellulose compounds, cross-linked cellulose compounds, acid-functionalized cellulose compounds, base-functionalized cellulose compounds, and combinations thereof. 